Fill in missing date and fill with the data above - r

Question

I've researched enough until i ask this here but can you please help me with some ideas for this issue?
My data table (df) looks like this:
client id value repmonth
123 100 2012-01-31
123 200 2012-02-31
123 300 2012-05-31
Therefore I have 2 missing months. And i want my data table to look like this:
client id value repmonth
123 100 2012-01-31
123 200 2012-02-31
123 200 2012-03-31
123 200 2012-04-31
123 300 2012-05-31
The code should be filling in the missing repmonth and fill the rows with the last value, in this case 200 and the came client id.
I have tried the following:
zoo library
tidyr library
dlpyr library
posixct
As for codes: ...plenty of fails
library(tidyr)
df %>%
mutate (repmonth = as.Date(repmonth)) %>%
complete(repmonth = seq.Date(min(repmonth), max(repmonth),by ="month"))
or
library(dplyr)
df$reportingDate.end.month <- as.POSIXct(df$datetime, tz = "GMT")
df <- tbl_df(df)
list_df <- list(df, df) # fake list of data.frames
seq_df <- data_frame(datetime = seq.POSIXt(as.POSIXct("2012-01-31"),
as.POSIXct("2018-12-31"),
by="month"))
lapply(list_df, function(x){full_join(total_loan_portfolios_3$reportingDate.end.month, seq_df, by=reportingDate.end.month)})
total_loan_portfolios_3$reportingmonth_notmissing <- full_join(seq_df,total_loan_portfolios_3$reportingDate.end.month)
or
library(dplyr)
ts <- seq.POSIXt(as.POSIXct("2012-01-01",'%d/%m/%Y'), as.POSIXct("2018/12/01",'%d/%m/%Y'), by="month")
ts <- seq.POSIXt(as.POSIXlt("2012-01-01"), as.POSIXlt("2018-12-01"), by="month")
ts <- format.POSIXct(ts,'%d/%m/%Y')
df <- data.frame(timestamp=ts)
total_loan_portfolios_3 <- full_join(df,total_loan_portfolios_3$Reporting_date)
Finally, I have plenty of errors like
the format is not date
or
Error in seq.int(r1$mon, 12 * (to0$year - r1$year) + to0$mon, by) :
'from' must be a finite number
and others.

Answer 1

The following solution uses lubridate and tidyr packages. Note that in OP example, dates are malformed, but implies having data with last-day-of-month input, so tried to replicate it here. Solution creates a sequence of dates from min input date to max input date to get all possible months of interest. Note that input dates are normalized to first-day-of-month to ensure proper sequence generation. With the sequence created, a left-join merge is done to merge data we have and identify missing data. Then fill() is applied to columns to fill in the missing NAs.
library(lubridate)
library(tidyr)
#Note OP has month of Feb with 31 days... Corrected to 28 but this fails to parse as a date
df <- data.frame(client_id=c(123,123,123),value=c(100,200,300),repmonth=c("2012-01-31","2012-02-29","2012-05-31"),stringsAsFactors = F)
df$repmonth <- ymd(df$repmonth) #convert character dates to Dates
start_month <- min(df$repmonth)
start_month <- start_month - days(day(start_month)-1) #first day of month to so seq.Date sequences properly
all_dates <- seq.Date(from=start_month,to=max(df$repmonth),by="1 month")
all_dates <- (all_dates %m+% months(1)) - days(1) #all end-of-month-day since OP suggests having last-day-of-month input?
all_dates <- data.frame(repmonth=all_dates)
df<-merge(x=all_dates,y=df,by="repmonth",all.x=T)
df <- fill(df,c("client_id","value"))
Solution yields:
> df
repmonth client_id value
1 2012-01-31 123 100
2 2012-02-29 123 200
3 2012-03-31 123 200
4 2012-04-30 123 200
5 2012-05-31 123 300